Beginners resist the idea of yielding and choose not to do it.
Consequently, they do not understand yielding and strictly speaking are not
training taijiquan anymore.
The resistance is psychological and comes from a poor understanding of the
physics involved.

Yielding is not simply about giving way when force is applied to you.
It
also concerns the matter of not applying force into a stationary object.
Taijiquan does not involve force against force. Consider
Newton's 3rd Law of Motion?

No feedback

If you were to push a person and they moved immediately, you would
experience no adverse feedback.
The person would be offering no resistance.
Your kinetic energy would encounter only surface pressure before continuing
unimpeded.

Rooted or resistant?

If you were to push a person and they did not move, you should not continue
to push.
Taijiquan advocates the use of gravity and balance. Allow your weight to
fall into the person.
Attempt to affect their balance on the horizontal or vertical axis.
This may not prove successful.
But then, it is not necessary to move a person in order to affect them.

Because the sage does not
struggle with world, the world does not resist.
An Ancient teaching says, "A winding path reaches its destination."
By yielding to the Way of the world, the sage is fulfilled by the world.

(Lao Tzu)

Striking

Taijiquan strikes should not be pushes. Karate may make contact and then
push. Taijiquan does not.
The key to not pushing is stopping as soon as you experience resistance.
If your body is pliable, you will not want to push or use your arms
for strength.

Not pushing

Our class places great emphasis upon not pushing.
We regard pushing to be a folly common to beginners.
Once you can feel the difference between using your weight and pushing, it
is easy to realise why.
If you wish to harm the person, you simply strike by dropping your weight
and allowing the surface pressure to bounce your hand away.
Do not try to strike through a stationary person.

Unbalanced

Yielding teaches you how to capitalise upon incoming force and strike a
person when they are unbalanced and/or moving.
Your aim is to maintain a discordant relationship with the assailant such
that they are unable to find their balance or find your centre in turn.

Yielding is used to evade punches, kicks and grapples. You also use it to
escape from locks and holds.
Instead of resisting or blocking force, you relax and create space. This
concept is usually introduced in your very first night in our class.
The space is both physical and psychological; it gives you time to move and
helps you to remain composed.

One of the 13 postures is called 'withdraw'. It exemplifies yielding.
The principle is simple: you evade the attacker by re-positioning yourself.
By creating a more favourable situation, you give yourself more choices
whilst reducing the attackers.

Withdrawing...

You do not retreat.
You do not go anywhere as such.
You simply change the nature of your relationship.
You allow your attacker to go where they want to go.
You do not resist.

Extremities follow the centre

Beginners often move their arms first. This is an external habit.
The body/torso must move first, and the arms and legs follow.

The
fastest, most powerful hand movements are the ones that use no strength.

(Cheng Man Ching)

Stepping

Poor footwork will not allow you to yield skilfully if the attack is
overwhelming.
A common mistake is to have the weight equally distributed between both
legs; it prevents smooth stepping and relaxed footwork.
Over-stepping or under-stepping are equally problematic, as is any attempt
to adopt a formal stance.
Low squatting stances are an encumbrance to movement.
You must move naturally and freely.

Respond to the space

Do not watch the attacking limb. Keep your gaze expansive and move when the
attacker moves.
Respond to the movement of the body. Watch the space occupied by them.
If you do not adhere to this approach, you will not yield in time and become
flustered.

Offer no purchase

Yield your own body until you emulate water. Do not become stuck, rigid,
fixed or held.
Remain soft and loose, flexible. If somebody tries to hold you - step. Step
repeatedly if you need to.
Withdraw your body and remove the limb your attacker is seeking.
When you are skilled at stepping, stop stepping and find space within your
body.

Gravity

Let your limbs be heavy and loose; like flaccid tentacles - boneless and
solid. Use gravity skilfully.
Without yielding, you cannot employ gravity.
Groundpath is not the same as connection. It requires you to place your body
weight in your hand.
If you want to increase your striking power, yield even more. Use less
strength.

No whole-body strength

New starters do not possess whole-body strength and find that the system
fails them in combat application.
They crumple.
This is to be expected.

Wrong means

Instead of training qigong and neigong, the new starter uses local muscular
tension instead and resist.
This is clearly not taijiquan.
Yielding will not work for somebody who lacks whole-body strength.
If you are struggling to gain whole-body strength, look to qigong and
neigong to build your strength.

Accepting whole-body strength

If you have been in the taijiquan syllabus for 6 months or so, you should
have developed some whole-body strength.
All of our exercises involve neigong.
This means that you can stop using tension and start doing taijiquan instead.
Unless you can see this fact, you will continue to use unnecessary force.
Once you 'get it', you will yield to everything and finally be using taijiquan.

Whole-body strength

Whole-body strength means that you can move your limbs and body without
tensing at all and have strength.
You can be soft, smooth, sensitive and pliable.
The doing is over. You trained 'doing' in qigong, neigong and form. In
application, focus upon 'not-doing'.

If your opponent is bigger than you or using
strength it should be to your advantage.
Use four ounces to deflect a thousand pounds and then borrow his strength.